Technical Field
The described technology generally relates to electronics, more specifically, to transimpedance amplifiers and associated switch networks.
Description of the Related Art
In high-impedance current producing sensor interfaces, a transimpedance amplifier (TIA) may be used to convert a relatively small current signal to a relatively large output voltage signal. For example, an input current signal, such as photodiode current signal, can have a wide dynamic range from less than about 1 nano-Ampere (nA) up to greater than about 10 milli-Ampere (mA), depending on the intensity of the incident light at the specific frequency of excitation. Using a fixed gain TIA, it may be desirable to have a high resolution ultra-low noise signal chain to process the signal further. A network of parallel resistor banks having respective switches or relays in series may be used to dynamically change the TIA gain to resolve the output signal in the correct signal range. Such a switch network, however, can suffer from various sources of error, as the switch resistance in series with the gain resistance can lead to a variation in the gain of the TIA over supply, temperature, and process variations. Furthermore, typical implementations using series relays can be bulky and/or can be difficult to integrate with the TIA.